The present disclosure relates generally to x-ray tomography systems and, more specifically, to a tiltable gantry for x-ray tomography systems.
X-ray tomography systems have been used for many years to create images of cross-sectional slices of subjects, such as human patients, and are particularly used as a medical diagnostic aid. Computed tomography (xe2x80x9cCTxe2x80x9d) scan systems usually include an annular gantry including an outer ring secured to a stand and an inner ring mounted for rotation within the outer ring about a centrally located spin axis of the gantry.
The gantry is typically about six (6) feet in diameter and the inner ring carries x-ray tomography components, which can include an x-ray tube for providing the x-ray beam, an anode for acting as the focal spot for the x-ray beam, one or more high voltage power supplies, balancing weights, a data acquisition module, and a bank of detectors diametrically opposed from the x-ray source, or focal spot. Some of these components may be secured in the outer ring of the gantry; however, at least some are secured in the inner ring for rotation therewith.
A platform, such as a table, is positioned horizontally through the center of the annular gantry, generally in alignment with the centrally located spin axis of the gantry, so that a subject to be x-rayed or scanned is supported on the table between the x-ray source and the bank of detectors. The inner ring of the gantry then rotates about the subject during the scanning procedure and the gantry may be adapted to move axially with respect to the table during and/or between successive rotations of the inner ring. In addition, it may be desirable to precisely tilt the gantry about a tilt axis normal to the spin axis so that the spin axis of the gantry is made parallel to, as well as aligned with, the subject to be scanned.
Moreover, because of the relative size and weight of the gantry and the x-ray tomography components supported therein, moving the gantry from place to place and maintaining and servicing the components mounted therein can be difficult. Although the inner ring of the gantry can be rotated to bring a component of interest within reach, it may be necessary or useful to tilt the gantry forward or backwards so that all components are easily accessible, or so that the x-ray tomography system can be moved from room to room without requiring its disassembly or that of surrounding structures.
Some mechanisms for tilting the gantry of an x-ray tomography system simply comprise a pivot arm linked to the gantry at the location of the pivotal mounting of the gantry to the stand. An operator can then tilt the gantry by applying torque to the pivot arm. However, because of the considerable size and mass of the gantry, tilting the gantry in such a manner requires significant torque, which can be relatively difficult for a single operator to provide.
U.S. Pat. No. Re. 36,415 to McKenna, entitled xe2x80x9cX-ray Tomography System with Gantry Pivot and Translation Controlxe2x80x9d, shows an improved, portable x-ray tomography system wherein tilting movement of the gantry is precisely controlled by mechanical displacement means which, in turn, are coupled to electro-mechanical means for monitoring the amount of tilting.
In particular, McKenna shows an annular gantry pivotally secured at arms extending radially outwardly from the gantry such that the gantry can tilt about the arms. A short member has an end fixed to one of the arms, and a ball nut is secured to the other end of the member. The member and the ball nut remain stationary while allowing elongated screw element to move through the ball nut as a reversible motor rotates the screw element. The motor is mounted on an outer frame of the gantry, close to the pivot arm, and the screw element is suitably journaled in the outer frame so that the screw element freely rotates without moving longitudinally with respect to the outer frame. As the screw element rotates, therefore, the entire outer frame (and therefore the entire gantry) tilts about the arms. The screw element is also journaled in the outer frame so that the screw element can pivot about the motor as the gantry tilts.
An x-ray tomography system having a tilting gantry, wherein a relatively small, force is required to tilt the gantry would be an advancement in the art.
The present disclosure accordingly provides a frame having a tiltable gantry for an x-ray tomography system. The frame, includes a stand having two arms, and an annular gantry positioned between the two arms and having an outer support pivotally mounted to the arms for tilting of the gantry about a tilt axis extending between the arms. An inner support is rotatable within and with respect to the outer support about a spin axis of the gantry that is substantially normal to the tilt axis, and the inner support is adapted to hold x-ray tomography components for rotation therewith.
The frame also includes means for applying a force to the gantry at a substantially outermost circumference of the gantry so as to effect tilting of the gantry about the tilt axis. The frame provided by this disclosure requires a relatively small force to effect tilting of the gantry.
According to one aspect of the present disclosure, the means for applying a force to the gantry comprises a tilt guide secured to one of the gantry and the stand at the outermost circumference of the gantry, and a drive mechanism secured to the other of the gantry and the stand for applying the force to the tilt guide.
The present disclosure also provides a method of conducting x-ray tomography including positioning a subject coaxially within the annular gantry of an x-ray tomography device so that the subject substantially intersects the coaxial spin axis of the gantry. The inner support of the gantry is then rotated about the spin axis, x-rays are emitted radially inwardly from the rotating inner support, and the x-rays passing through the subject are detected. The method also includes applying a force to the substantially outermost circumference of the gantry prior to emitting the x-rays so as to effect tilting of the gantry about the tilt axis until the spin axis of the gantry is substantially aligned with the subject.
Other advantages of the presently disclosed frame with tiltable gantry will become apparent by reference to the following detailed description taken in connection with the accompanying drawings.